1. Field of the Invention
The present invention relates to a technical field of an ink jet recording apparatus that records an image on a recording medium by ink jet system using ink where color particles (colorant component) are dispersed in a solvent (dispersion medium). More specifically, the present invention relates to an ink jet recording apparatus that is capable of efficiently collecting solvent vapor generated from the ink.
2. Description of the Related Art
An electrostatic ink jet recording system is a system in which ink containing color particles, such as pigments, charged and dispersed in a solvent is used and an image corresponding to image data is formed on a recording medium by ejecting the ink (droplet) by means of an electrostatic force through application of a predetermined voltage to each ejection electrode of an ink ejection head in accordance with the image data. Then, the image formed on the recording medium by the ejected ink is, for instance, heated using a fixing means, thereby removing the solvent component of the ink and fixing only the color particles on the recording medium to record. Here, the ink forming the image on the recording medium contains concentrated color particles and solvent component, so that it is required to vaporize/dry and remove the ink solvent component and to fix only the color particles on the recording medium by the fixing means, for instance, a heating means or the like.
In an ink jet recording apparatus adopting such a recording system, solvent vapor is generated in an ink ejection portion, a fixing portion (in particular, a heat-fixing portion), or the like as a result of the vaporization/drying of the ink solvent component. An organic solvent is used as the ink solvent component and the emission thereof to the outside of the apparatus leads to environmental pollutions. Therefore, it is required to collect and remove the ink solvent component within the apparatus.
For this purpose, with a method conventionally and generally used in the ink jet recording apparatus, a solvent collecting device is provided in the apparatus, air in the entire region inside the apparatus is taken infusing the solvent collecting device, and the ink solvent component is collected/removed by absorbing the solvent component using a solvent adsorption material or concentrating the solvent component through cooling of the taken-in air.
However, the solvent collecting device used in the conventional ink jet recording apparatus takes in air in the entire region inside the ink jet recording apparatus, so that there is a problem that, in addition to air containing the solvent component, the solvent collecting device simultaneously takes in air containing a small quantity of the solvent component, such as the atmosphere (air in an installation environment) or the outside air flowing into the apparatus, and then a vapor concentration of the solvent component contained in the taken-in air is low, therefore the collection efficiency is decreased. In addition, water vapor contained in air inside and outside the apparatus exerts an innegligible influence on the collecting of the solvent component. In particular, a water vapor component in the taken-in air causes lowering of the collection efficiency of the solvent collecting device that collects the vapor of the solvent component, which leads to various problems such as an increase in size of the solvent collecting device, an increase in power consumption, and lowering of maintainability. Also, not only the solvent component but also the moisture is simultaneously collected, so that there is another problem that it takes a lot of trouble to reuse the solvent. Further, the air in the entire region inside the apparatus is taken in, so that particularly when the heat of the heat-fixing portion is easily transmitted to the ejection head or when air from the heat-fixing portion flows to the ejection head, the ejection head is easily dried, which leads to still another problem that ink clogging occurs due to the drying of the ejection head or ink ejection stability is lowered due to changes in viscosity of the ink.
Meanwhile, in order to suppress or prevent vaporization of a solvent component from ink forming an image on a recording medium in an ink jet recording apparatus, there have conventionally been proposed some methods for removing the solvent component from the ejected ink without allowing the solvent component to be vaporized. In JP 06-126945 A, for instance, a transfer type ink jet printer is disclosed in which color particles in ink ejected onto a transfer drum are separated from a solvent by means of an electrostatic force and are temporarily fixed on the transfer drum, the solvent is selectively absorbed/removed from the transfer drum by abutting a roller-like solvent removing means made of a material absorbing only the solvent against the transfer drum, and the color particles on the transfer drum are transferred onto and fixed on a recording medium.
With the printer disclosed in JP 06-126945 A, however, in addition to the transfer drum, the specially designed solvent removing means that absorbs/removes the ink solvent under a liquid state needs to be provided before a position at which an image formed by the ejected ink is recorded on (transferred onto) the recording medium. Therefore, there is a problem that the apparatus construction becomes complicated and the apparatus size is increased. Also, the ink forming the image on the transfer drum is mainly composed of the color particles and it is difficult to completely remove the solvent component from the ink, therefore when the printer is continuously operated or a large amount of print is outputted, there is another problem that it is also required to remove the solvent component vaporized from images transferred onto recording media.
Also, as a method of circumventing a situation where vaporization of an ink solvent on a print medium continues for a long time, JP 11-320856 A discloses a liquid ejection printer in which vaporization of a solvent of ink ejected onto a print medium is accelerated using a means for forcibly vaporizing the ink solvent by heating the ink on the print medium in a non-contact manner immediately after recording on a print medium transport path, by sucking air around a surface of the print medium immediately after recording, or by reducing a pressure in a cover box provided so as to cover the whole of the print medium transport path at a position immediately after an ink ejection portion. JP 11-320856 A also discloses a liquid ejection printer that includes a means for collecting an ink solvent by absorbing the ink solvent using an absorbing agent provided inside a cover box provided so as to cover an ink ejection portion and the whole of a print medium transport path, a means for collecting the ink solvent by coagulating (concentrating) and liquefying ink solvent vapor through cooling of air inside the cover box using a cooling apparatus provided inside the box, or the like. JP 11-320856 A further discloses a liquid ejection printer that includes a means for forming a layer of hardener by spraying a hardener serving as an ink vaporization suppression agent onto a print medium immediately after recording.
With the technique disclosed in JP 11-320856 A, however, in the case of the printer that circumvents a situation where vaporization of a solvent of ink ejected onto a print medium continues for a long time using the means for heating the ink on the print medium in a non-contact manner immediately after recording on the print medium transport path or the means for sucking air around a surface of the print medium immediately after recording, there is a problem that it is impossible to collect the ink solvent vaporized as a result of heating or sucking. Also, in the case of the printer including the cover box that covers the whole of the print medium transport path or the ink ejection portion as well as the whole of the transport path, there is a problem that the apparatus construction becomes complicated and the apparatus increases in size. Further, in the case of the printer that accelerates the ink solvent vaporization using the heating means or the sucking means provided immediately after the ejection head or the printer that uses the cover box that covers the whole of the print medium transport path and the ink ejection portion, there is a problem that drying of the ejection head or changes in viscosity of ejection ink may exert adverse effects. Also, in the case of the printer including the means for forming the layer of the ink vaporization suppression agent on a print medium immediately after recording, there is a problem that the cost of outputted prints is increased.